Interlocking system for railroads



Sept. 22, 1931. N. DONOVAN INTERLOCKING SYSTEM FOR RAILROADS Filed Dec. 5. 1929 2 Sheets-Sheet l ms m N Y on B wm an mu {4 mm 1Q m0 Vm W W 6 6 E lm 1| 1| II}. n NM. um nn MN IQ. rNm m- MJ I. WE h |l| ll l. wfiw nm 3 Om m d T3 HQ MN m L I I I I I I QM Fr 7 9 H2 2n an I? p 0Q 3 I I z a v FA Sept. 22, 1931. N. L. DONOVAN INTERLOCKING SYSTEM FOR RAILHQADS Filed Dec. 5, 1929 2 Sheets-Sheet 2 QM km .IIIIIBPII Patented Sept. 22, 1931 UNITE, STA-res Pare NT omen NORMAN L. Donovan, or JERSEY CITY, NEW JERSEY. ssxenon. TO-GENERAL RAILWAY SIGNAL COMPANY, ornocnnszrnnnnw YORK rnrnntocxme SYSTEM: non nAILRoAns Application filed December 5, 1'929.*Seria1: 1N0; 411,823.

This invention relates to interlocking sys= terns for railroads, and more particularly pertains tocircuits and devices used to accomplish the control oi the switch machines 5 employed in such interlocking systems,

In an interlocking plant, it is desirable to control the various traffic control-ling iunctions from a. central tower, so that the traffic may be as-nea-rly as possibletnider. the supervision of a single operator. However, the

usualtype of interlocking machine, employed in the interlockingtower to-control the distant trafiic' controlling functions, sometimes assumes such a size as torequire several opemtors or leverm'en toactunder the orders ot a single supervisor. 2' Also, this type of interlocking machine has the control levers interrelated by the usual mechanical intcrlockmg' betweenlevers as well as conzo tain-ing the various'circuit controllers, se-

lectors,time cont-actors, indication latches, and the like, which add to the bulk ot the machine; v 1 V The present invention proposes to provide 2; an hiterlocking. system with awtype of ce11- tralized controlthat may be conveniently termed push buttoncontrol which provides a. great economy in space for the controlboa-rd and multiplies the number of funceo tions which one operator. may adequately supervise. The present invention provides that the circuit controllers, locks, selectors, and the like, maybe located in a room or building adjoining the operating roonr, a; A furtherobject-ofthe invention is to provide this type of push button control and stillemploy the principles of control which are used with the four position typecontrol lever in connection with the operation of. power operated switchmachines. This object is accomplished by the provision ofsuitableelectromagnetic circuit controllers and locks both in the central tower and at the switchlocations, and indication means ind-icating the completion of an operation of a track switch as well as its 'position and. locked'eondition, r l e Other objects, purposes andcharaeteristic teatures of the present inventionwill be in part. obvious fromtheaccompanying draw:

ings, and in partpointed out. as the descriptionof the invention progresses. I l

I11 describing the invention in detail, reference wlll be madetothefiaecompanymg drawings, inwhich Figs. l and 1A, when 5 placed end toxen'd, represent in a -diagram-. matic manner the circuitsand devices arranged and constructed according to r the present invention to accomplish thecontrol of a single. track switch, I;

With reference to the accompanying-dram ings,.a track. switch TS is shown as operated by a suitableswitchmachine SM which may be. of the, type, for example, such as shown in the patent-to K. Howe No. 1,466,903 5 dated September :4, 1923. This switch ma-. chine SM isshown in. the conventional man-:- ner as includingan armature A,,a field wind; ing F, pole changercontacts. PG, pole changer coilcontacts FCC, and point detector cone t acts PD. This switch machine operates a manner as set forth in the abovementioned Patent No.. 1,466,903 with, its operating circuits adapted to the present invention- The pole changercontacts PC include 7 5 movable contacts 5 and 6 which make connection between certain pairs offixed contacts. whenin normal. positions and between certain otherrpairsof fixed contacts when in reverse positions. These movable. contacts 5 and '6 are caused to assume normal positions at the end of the operation of the switch machine to a normal position, and are caused to assume reverse positions at the end of the operation of the switch machine to a reverse position, orare operatedto an opposite extreme position during mid-stroke of the switch machine dueto thereversal of the control, which is accomplished suitable .energization of the pole chang r. coils '7 and 8. r

The .polechanger coil contacts PCG'include'movable contacts 9 and 10. Themo'w able contact 9 makes contact between a' pair of fixed contacts when in'anormal position or when inan intermediate position, while the movable contact 10 makescontact' between 21: pair of fixed contacts-when in a reverse position or when in an intermediate I position. These. movable contacts 9 and 10- 1 assume normal or reverse positions in correspondence with the swltch machlne SM, and

assume intermediate positions during the These contacts 14: and 15 make contact between their respective pairs of fixed'contacts when in normal extreme positions, and make contact between certain other pairs of fixed contacts when in reverse extreme positions. i

Located at the'switch machine is a remote controller RCR for governing the'supply of operating energy to the switch machine SM from a local source of electrical potential, the positive and negative terminals of which are conveniently designated B+' and B- respectively. The remote controller RCR is provided with normal and reverse operating coils 16' and 17 respectively which operate a contact rod 18 to either of two extreme positions depending upon the coil last energized. This contact rod 18 carries movable contact members which make connection between their respective pairs of fixed contacts either when in normalpositions or reverse posltions as will be more specifically I pointed out hereinafter. The contact rod 18 is provided with a projection 18 which is engaged by a lock rod'l9 that is operated to a non-engaging position by a lock coil LC and is returned to an engaging position by either of two indication coils 21 or 22. The lock rod 19 may engage the projection 18 when it is in either normal or reverse position, maintaining the contact rod 18 in such position until the lock rod 19 is actuated to a non-engaging. position. Thislock rod 19 further carries movable contacts which make' contact between their fixed pairs of contacts either with the lock rod in a normal locking position or in an unlocked (non-engaging) position in accordance with the function to be accomplished.

It will be noted. throughout the description of the embodiment of the present invention, that the opposite terminals of all sources of electrical potential will be designated as 13+ and B, which sources may be the same sources of supply or other suitable sources all in accordance with the practical application of the invention. It is to be understood that these sources of electrical'pptential for operation of the switch machine SM and other devicesare preferably local to the switch machine and the points indicated; also, they may be of either direct current or alternating current according to the circumstances to be met in practice.

In the interlocking tower, a miniature track diagram, identical in every respect to the actual track layout in the interlocking plant, is shown as including the track switch ts beneath which are normal and reverse indicator lamps N and B respectively which indicate the position and locked con- "dition of the associated track switch TS.

Beneath these two indicator lamps N and R are'located two self-restoring push buttons PN and PR having restoring means, as springs s, which accomplish the controlof the track switch TS to normal or reverse positions respectively.

Aselector S of the electromagnetic mechanical stick type is provided for maintaining the condition established by the momentary depression of either of the two push buttons PN and PR.

The actualcontrol of the distant remote controller RCR and switch machine is accomplished by a circuit controller CR which may be located at any convenient point in the interlocking tower and includes normal and reverse operating coils 24 and 25 respectively for operating a contact rod 28 to either of two extreme positions. This contact rod 28 carries movable contacts for interconnecting their respective pairs of fixed contacts in accordance with the positions as sumed, as hereinafter described. The lock rod 28 carries a projection 28 which is engaged by a self-restoring locking member 29,'that is, the locking member 29 normally assumes an engaging position due to some suitable biasing means, shown as a coil spring, except when actuated to a non-engaging position by a controller lock coil 30. This locking member 29 also carries a movable contact for making contact between a pair of fixed contacts when in a normal biased position and between another pair of fixed contacts when in an actuated or unlocked position.

Also, located in the interlocking tower, is a relay SS for indicating the position and locked condition of the associated track switch TS, the correspondence with said track switch TS of the remote controller RCR, and the completion of an operation of the switch machine. This SS relay has associated therewith arepeater relay SR for purposes to be hereinafter set forth.

Y A look relay LR is controlled by the track repeating relay TR associated with the track section in which the track switch TS is located, and by the various other sectional locking and route locking relays (not shown) usually employed for electrically interlocking the various trafiic controlling functions of interlocking plants.

It is believed, that the usefulness and the various interrelated functions of the devices and circuits oi this specific embodiment of the present invention will be more readily understood "further description being given from the; standpoint. of operation.

fOpemtion {the system, n The interlocking system is shown in a ninnormal position with. the track switch TS 131 afnnrmal locked position, .NVlilll-Qlll is inrli.-,

caztedsin the, interlocking towerrhy: the i1 lumination of the indicator lightN located beneath the track: diagram; The remote" con;- troller B-CR is in :arnormal locked "condition which prevents the switch machine from being operated, due to, the dynamic indication circuit, untilJthe-lock coil LC has beencproperlly energized. This: cannot occur unless. the lock relay LR located in the in.- tcrlock'rng tower .is' energized, when push hirtton for controlling the track switch TS to anew positi'om'is"depressed I wires it-Brand contacts 6-45, wires 46 and 47, to; the lower teianinal of the armature A. The lock. rod 1 9 is in an. engaging positionimrespect to the contactrod 18, as a result ot which cnergyfis applied to. the: pointdctector contacts PD" which i nclicate the; none mal position: and locked conditionof track; switch-TSLhy energizing the SS relay in the interlocking tower fwith current of a; normal polarity This normal energizing circuit for the SS: relayis traced as iollows=r-firo1ir the positive terminal :of a suitable sourcev o l? electrical potentialindicatcd as Bi+ through normal con-tact 50 of remote controller RCR, wires 51. and 52, contacts 1 2-54, wires 55; and 56, Winding of SS relay, Wire 5:7,.co1rtacts15-58-, wires 59-and 6l-).-,.nor1nzal con-tact 6-1 of remote controller- RCR, tothe negative terminal of thesu-itable source indicated as the SS relay toright-hand normal: positions Cal results in the cnergizatiom of the and the indicator-lamp- N.. a

The energization of? the contacts of attraction of. the: 94E of relay SR :dfienergizesthc; circuit. for the lock coil. 30, which in turnf allows the energization oil the normal indicator lamp N. The energizing circuit for the indicator lamp N is traced as follows:from: the positive. terminal; oil 1" a suitable source of electrical potential indicated; as 3+, througl'i. flout contact 'ZI-oii lock relay LR,*wire 72, normal contact '73 of relay SS wire 74, hadicator lamp N, wire 75, normal contact 76 of controller GR,;to

the negative terminal of the suitable. source 7 indicated as B; r

It be noted, throughout-the descriptikanof the" specific embodiment of the present invention, the lock relay LR is assumed to-he energized in accordance with proper conditions ot the detector track section associated witlr thetrack' switch 'ISJand' I the various othersectional and route lockmg rel'a ysassociated therewith. Thelcck relay LR is she-Mm toindicate the point of? interconnectionbetween the present inven tion and the interlockmg circuitsz of usual pnactice to be associated: therewith.

Letv us now assume thattheioperator de sires-to operate the track switch from a normal locked position to a reverse-locked posie ti'on To ac'complish this result, the open ator' depresses the push button PR3 which actuates' thercontacts oi? the selector S to reveise positions if the lock relay LR is properly energized according to the condi-. than of the associated detector track sections and route" locking relays and the like. As soon as the selector is operated, energy is placed upon the wire 88" which energizes the lock coil LC; the same time,the opera'. tionof the selector contacts to reverse positions: opens the energizing'circuit of the: re lay S-R'whi'ch, when deenergized, energizes the lock coil 30 of the controller CR if the lock relay LR is still energized; This actuates the locking member 29- to a non-engaging" position closingthe circuit at that time for thereverse operating coil- 25 of the controller" CR. The contact rod 28 is then operated to areverse posit-ion closing a circirit for energizing the reverse operating coil 17" of the remote controller RCR (forthe circuits involved, see' bel'ow). As the lock rod 19 ofthe remote controller-KGB is now in an energized position, the contact rod I8 is operated to reverse position. Thus, energy is placed uponthe reverse operating Wire ofth-e switch machine SM' which causes" it to operate the track'switch TS to a re; verselocked position.

When: the switch machine has completed the operation of the track 1 switch, ithas free movement. or .free run at the. end of the operating stroke which generates a dy= current that flows through the coil: 21 to'actuate the lock rod 19 back to-an engaging locked position, as: Well as dynamicontact rod 28 of the controller GR in a reverse position. I 1

Considering the operation in greater detail, the energizing c1rcu1t for the reverse operating coil of the selectorS is traced as follows:-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 71 of lock relay LR, wires 71. 78, 79 and 80, depressed push button PR, wire 81, reverse operating coil 820i selector S, to the negative terminal of the suitable source indicated as B. The contacts of: the selector S are operated to reverse positions, which results in the deenergization ofthe relay SR with its circuit as heretofore traced opened at normal contact 64 of selector S. Also, as soon as the contact 64 of selector S reaches a reverse position, a circuit is completed for energizing the lock coil LC of the remote controller RCR. This energizing circuit for the lock coil LC is traced as follows :from the positive terminal of a suitable source of electrical potential indicated as B+, through reverse contact 64 of selector S, wires 84 and 85, normal contact 86 of controller CR, wires 87, and 88, winding of lock coil LC, wires 89 and90, front contact 91 of lock relay LR, to the negative terminal of the suitable source indicated as 13-, The lock rod 19 is operated to a non-engag ing position opening the normal energizing circuit of the SS relay at normal contacts 50 and 61 and closing a circuit for energizing the reverse operating coil 17 of remote controller RGR as soon as the controller OR is operated to a reverse position.

The energization of the lock coil 30 of the controller GR is completed, as soon as relay SR is deenergized through a circuit traced as follows :from the positive terminal of a suitable source of electrical po* tential indicated as B+, through front contact 71 of lock relay LR, wires 78 and 92, lock coil 30, wire 93, back contact 94 of relay SR, wires 95 and 90, front contact 91 of relay LR, to the negative terminal of the suitable source indicated as B". The locking member 29 is actuated to a non-engag ing or unlocked position in which the normal contact 76 is opened and unlocked contact 76 is closed which energizes the re verse operating coil 25 of controller CR to operate the contact rod 28to a reverse position. V v,

The reverse operating circuit of the con-v troller GR is traced as follows :-V-from the positive terminal of the suitable source of electrical potential indicated as B+, through, unlocked contact 76 of controller CR, wire 96, reverse contact 97 of selector I 'whichwopens the energizing circuit for the lock coil LC at the normal contact 86 and closes the energizing circuit for the reverse operating coil 17 of the-remote controller RCR at reverse contact 100. r

The reverse energizing circuit for the remote controller RCR is traced as follows from the positive terminal of a suitable source of electrical potential indicated as B+, throughreverse contact 100 of controller CR, wire 101, reverse operating coil v 17 of remote controller RCR, wire-102, unlocked contact 103 of remote controller RCR, wires 104, 89 and 90, front contact 91 of lock relay LR, to the negative terminal of the suitable source indicated as .7 4;

B The contact rod 18 of remote controller RCR is operated to a reverse position in which the reverse operating circuit of the switch machine SM is completed causing it to operate the track switch TS from a normal locked position to a reverse locked position in the usual well known manner.-

The reverse operating circuit of the switch machine SM is traced as follows :from the positive terminal of the suitable source of electrical potential indicated as B+, through reverse contact 107 of remote controller ROB, wires 108, 36 and 35, contacts -34, wire33, armature A, wires 47 and 46, contacts 6-45, wires 44 and 43, field winding F, wires 42, 41 and 109, reverse contact 110 of-remote controller RCR, to the negative terminal of the suitable source indicated as B. The switch machine SM now operates, and as soon as the track switch TS is unlocked, the movable contacts 9, 10, 14 and are operated tointermediate Positions. w i I Vith the movable contacts 9 and 10 of the pole changer coilc'ontacts POO in intermediate positions, the switch machine SM could be reversed in mid stroke as the movable contact 10 closes a circuit which, if energized by the remote controller RCR, wouldenergize the pole changer coils 7 to operate the movable contacts 5 and 6 to reversed positions to cause the switch machine to operate in an opposite direction. This is accomplished in the usual manner and need not be explained in detail.

Assuming that the switch machine SM continues to operate the track switch TS, the movable contacts 5 and 6 are operated to extreme reversexpositions at thecomplethrough the indication [coil tlon arm ment-mg stroke, while the mov-' able contacts 9, .10, 14 and 15- are operated to reverse extreme positions as ,soon as track switchTS .is locked. 1

When the movable contactsv 5 and Breach their reverse extreme positions due to their operation by "the switch machine SM, :a'reverse snubbing or dynamic braking circuit is completed, whichcauses energy. to flow This circnit, as well as braking the motor of the switch machine, also serves to operateathe lock rod 19-to an engaging position which prevents any further movement of the contact rod 18 olremote controller RGR, until it is again unlocked." V I This reverse dynamic braking or snubbin g circuit for the remote operation of the switch machine SM is traced as tollowsz -from the upper terminal of the armature A, through wires 33 and 111', contacts i5-11 2, wires 113, 11 i and 11 5, indication coil 22,wlire 116,- reverse contact 117 of remote controller 11GB, wires 118, 119, 120 and 43,: held winding F, wires42 and 121, contacts '6122, wire 47 to the lower terminal of armature A.. The dynamic current of' the switch machine fiows in indication coil 22 and is effective, as heretofore mentioned, to operate the lock rod 19; The energizing circuit. for the reverse operating coil 17 of remote controller RGR' is now opened at wun locked contact 103. As the movable contacts 14 and of the-point detector contacts PD are reverse extreme positions energy is applied to the-SS relay through a reverse energizingcircuit with the oontactsfil and '50 in normal-positions- This reverseenergizing circuitforthe SSrelay is traced .as followsvz-from the positive terminal of a suitable source of. electrical potential indicated- .as 3+, through normal contact 50' of remote controller RCR, wire 51-, contacts 15-123, wires 124 and 57,iwinding of SS relay, wires 56 and 125, contacts 14-126, wire 66, normal contact 161 of reniote controller BOB, tothe negative termi-- nal of the suitable. sonrce indicated as 13+. The contacts :68. and? 3 0i? the SS relay are thus energized to reverse left-hand positions in which the reverse energizing circuit for the relay SR is completed. The reverse energizing circuit for-relay SR istraced as follows :.-fromthe positive. terminal of :a suitable source of electrical potential indicated as Bl-, through reverse contact 64 of selector S, wires .84 and 128, reverse contacts129 of controller "GR, wire- 130, reverse contact 68 of relay SS, wire '69, winding of relay SR, to: the negativeg-terminalcof the suitable source indicated :asrB,1 I The contact 94 of relay SR'i's actuated foo-an energized position which opens the energizing circuit of the look coil 30 of the controller GB at back contact 94 rasis obvious from the drawings The locking member 529 *oif'control'ler CR now assumes a locked position. 'engaging the contact rod 28 preventing its movement. The energizing circuit for the reverse operating; coil 25 oi the controller GR is opened at unlocked? contactilfi, while the-energizing circuit tor the indicator lamp R .is now completed with the .SSrelay indicating indicator lamp R' is. traced :as follows from the positive terminalxof a suitable source of electrical potential; as

13+, throng-h front contact 71: of relay L5H,

wire 72, reverse contact 7 3 of-relay f-SS, wire 13-1., indicator lamp R, wire 75, normal contact 76,;to the negative terminal of the suitable source, indicated as B The operation, of the interlocking sys tern shown as the specific embodimentv of I I the present invention, has been. described from its normal condition to its reverse condition which is deemed sulficient to point out the features of the present invention without describing the operation of the sys lock rod 19. to an unlockedpositioncluri-ng the time-that the relay SR is becoming olethe reverse locked position o-f the track switch TS. This energizing circuit for the Too energized. However ,.shonld the distance between the controller theinterlocking tower and the remote controller RCR at the gswitch machine be so great that the action of the resistance and impedance of the line wires would Joe efieotiveas toreatard theactuation of lock rod 19 by lock Lcoil. LG, the relay-SR be made slow acting inaccordance therewith to provide 1" thatthelremote' controller RGR may posi tively beunlocked beliore the controller operates to-deenergize the lock coil LG.

- Hazving described one rather specific em bodiment of the present invention, it; is to he understood that the various circuits and devices, included within the embodiment, a are varying requirements of practice without departing from the spirit or scope of the invention as set forth in the appended claims.

flaming described my invention, I now.

claim:-

its

L Y 1. Inan interlocking system for railroads, a track switch, a switch machine having normaliand reverse operating circuits, electromagnetic contactor means for closing said normal or said reverseoperating circuit, and self-restoring push; button means for causing operation of said contactor'means.

2. In an interlocking system for railroads, a switch machine having a normaloperating circuit and a reverse operating circuit,'a twoposition contactor for closing said normal operating circuit when in one position and for -closing said i reverse operating circuit when in the other position, one self-restoring push button for opearting saidcontactor to one position, another self-restoring push bu"- ton for operating said contactor to the other position, and means preventingoperation of said contactor except in accordance with traflic conditions. 1

8. In an interlocking system for railroads, a switch machine having a normal operating circuit and a reverse operating circuit, a two-position contactor for closing said normal operating circuit when in one position and -for closing said reverse operating circuit when in 1 the other position, one

self-restoring push button for operating said contactor to one position, another self-restoring push button for operating said contactor to the other position, ,a looking member for preventing operation of said contactor, -means for actuating said locking member to a non-locking position, said means being operable in accordance with trafiic conditions when said one or said other push button is depressed, and means actuating said locking member to a locking position, said means being operated by dynamic current generated by the free run of said switchmachine.

4:. In an interlocking system for railroads, a switch machine having a normal operating circuit and a reverse operating circuit, a twoposition contactor 'for closing said normal operating circuit when in one position and for closing said reverse operating circuit when in the other position, a locking member for preventing'operation of said contactor, a lock coil for actuating said locking member to a non-locking position, means for actuating said locking member'to a locking position, said means controlled bythe dynamic indication current of said switch machine, one self-restoring push button for operating said contactor to one'position, another self-restoring push button for operating said contactor toan opposite position, and means associated with said one and said other push button for executing the operation of said contactorvto a new position asinitiated by eitherof said push buttons.

5. In an interlocking system for railroads, a switch-machinehaving a normal operating circuit and a reverse operating ei-rcuit,;a

two-positionfcontactor forclosing said normal operating circuit when .in one position and for. closing said reverse operating circuit when in thehother. position, a locking member: for preventing operation vof said contactor, a lockcoil for actuating said locking member to a non-locking position, means for actuating said locking member, to a look ing position, said means controlled by the dynamic indication current of said switch machine, ,a two-position mechanical stick type selector for. eperating saidlcontactor to one or the other of its positions, one selfrestoring pushbutton for operating said selector ,to one position, andanother self-restoring push button for operating said selector tothe other position. V

6. In aninterlo-cking system for railroads,

a switch machine having a normal operating circuit and .l a reverse operating circuit, a two-position contactor for closing said nor.- mal operating circuit when in one position and 1 for closing said reverse operating circuit when in the other position, a: locking member for l preventing operation of said contactor, a lock coil for actuating said locking member to a non-locking position, means for actuating said lockingmember to a look ing position, said means controlled by the dynamic indication current of said switch machine, a two position controller for operatingsaid contactor to one or the other of its positions,la lock normally preventing operation of said controller, means active to release said lockwhen said controller is out of correspondence with said contactor, a twoposition mechanical stick typerselector for operating said controller to one or the other of its positions,cone self-restoring push but-- ten for operating said selector to one position, another self-restoring push button for operating saidselector to the other position, means preventing operation of said selector except in accordance with traflic conditions, means energizing said lock coil when said selector is outs of correspondence with said controller, means indicating the position and locked condition of said switch machine, and means indicating the correspondence of said selector, said controller with said switch machine.

7. In an interlocking-system for railroads, a track switch, a switch machine having a normal operating circuit and a reverseoperating circuit, .one self-restoring,.normally open, push button forclosing said normal operating circuit, another like push button for closing said reverse operating circuit, and means for accomplishing the control of said switch machine as initiated by said one and said other push buttons 7 l 8. In an interlocking system for railroads, a track switch, a switch machine having a normal operating circuit and a reverse operating circuit, contacting means for closing said normal operating circuit and opening said reverse operating circuit when in at normal position or closing said reverse operating circuit and opening said normal operating circuit when in a reverse position, means for operating said contacting means to. a normal position, means for operating said contacting means to a reverse position,

. a lock normally preventing operation of said contacting means to a new position, means releasing said lock in accordance with trafiic conditions when said normal or said reverse operating means for said contact means is actuated, and means operating said lock to a locked condition, said means being actu-.

ated by the dynamic current of said switch machine.

In testimony whereof I aflix my signature.

' NORMAN L. DONOVAN.

DISCLAIMER 1,824,748.N0rman L. Donovan, Jersey City, N. J. INTERLooKrNG SYSTEM FOR RAILROADS. Patent dated September 22, 1931. Disclaimer filed February 16, 1934, by the assignee, General Railway Signal Company.

Hereby enters this disclaimer to claims 1 and 7 of said Letters Patent, which are in the following words, to wit:

1. In an interlocking system for railroads, a track switch, a switch machine having normal and reverse operating circuits, electro-magnetic contactor means for closing said normal or said reverse operating circuit, and self-restoring push button means for causing operation of said contactor means.

7. In an interlocking system for railroads, a track switch, a switch machine having a normal operating circuit and a reverse operating circuit, one self-restoring,

normally open, push button for closing said normal operating circuit, another like push button for closing said reverse operating circuit, and means for accomplishing the control of said switch machine as initiated by said one and said other push buttons.

[Ofllct'al Gazette Zllarch 13, 1934.] 

